Numerous substances must be isolated from the atmosphere and from contact with people, yet must be accessible for manipulation by humans. These materials include radioactive substances, toxic substances, and certain biological materials. Hoods and gloveboxes are often used to contain and isolate these materials when they must be handled, though certain highly radioactive materials must be isolated behind leaded glass as much as 50 cm thick and handled by remotely operated mechanical manipulators. The most common containment or isolation apparatus is a laboratory hood having an entirely open front and an exhaust fan connected to the rear or top of the hood. The fan causes air to flow into the hood from the open front toward the fan connection, thus tending to sweep material away from a technician facing the open front of the hood. A laboratory hood which is used when the degree of protection provided by the usual open-front hood is not sufficient has a glass or transparent plastic panel covering the face of the hood except for a portion which is open to allow a technician to insert his hands. Blocking a major portion of the hood face not only better isolates and protects the technician but allows the volume of air flowing into the hood to be decreased, thus decreasing the cost of the installation.
Gloveboxes are well known enclosures for isolating hazardous materials, particularly when radioactive materials must be handled. These boxes are completely sealed from the atmosphere and have gloves with long cuffs, or extensions, located inside the enclosure and connected to a wall of the enclosure. A small air flow through the box is usually maintained and both air entering the box and air leaving the box passes through HEPA filters. A technician inserts his hands and forearms into the cuffed gloves and then can manipulate materials and apparatus inside the box. Where the need for isolation is less critical, "open-front gloveboxes," or open-front containment boxes, may be used. Though the term "open-front glovebox" is inaccurate, it is commonly used. For example, a standard glovebox may be used for radioactive substances in the form of powders while an open-front glovebox is used for radioactive solutions. An open-front containment box is an enclosure having an opening without gloves attached to it through which a technician may insert his hands and, if necessary, his forearms to handle material within the box. The technician will normally be wearing protective clothing, such as gloves and a smock. An open-front glovebox is much more convenient to use than a conventional glovebox and its use allows a technician to work more rapidly. An open-front glovebox is normally maintained at a pressure slightly below atmospheric pressure by means of a fan which exhausts the air passing through the glovebox to the atmosphere. In most cases, a filter is provided at some point between the fan inlet and outlet to prevent toxic material which is pulled from the glovebox by the fan from entering the atmosphere.
In the manufacture of pharmaceuticals and electronic components such as chips, it is necessary to protect the product from airborne contamination. This is normally accomplished by working in "clean rooms" in which the air pressure is greater than atmospheric pressure so that air flows out of the rooms. The air provided to a clean room must be filtered and people entering a clean room must completely cover their normal clothing with smocks or "bunny suits" which do not shed particulate matter and often must wear face masks. For certain small scale operations, a containment box which is operated at a positive pressure by means of supplying clean air to it may be used.
The present invention is an improved material isolation enclosure, or improved open-front glovebox, or improved containment box, which is useful in either situation: where the material handled is toxic or where the material handled must be protected from atmospheric contamination. The invention will be explained primarily in terms of an enclosure connected to a ventilation system which maintains a negative pressure inside the containment box. Those skilled in the art will recognize that the invention is easily adapted to use of an enclosure which is operated under positive pressure. The present invention was developed in the course of design of a facility having several hundred open-front gloveboxes. The total amount of air flowing into several hundred conventional open-front gloveboxes requires a very large system of ductwork and fans. Also, all of this air must be passed through HEPA filters, which are extremely expensive, before being exhausted to the atmosphere. Use of the present invention will enable the air volume handled to be reduced by a factor of 3 or 5 or more. This allows much smaller ducts, fans, motors, and filters to be used. In the case of a clean room-type containment box, it can also be seen that the volume of air required to be supplied to the box and the required air handing apparatus will be greatly reduced by use of the present invention.